Chloride Ion Penetration Test Research Articles

Properties of Concrete with Waste Glass Powder (Gp) as Fine Aggregate Replacement

In the present research, the feasibility of using waste glass as replacement for natural river sand was investigated. Glass wastes dumped in landfill pose environmental pollution and research on its reuse in construction industries need to be carried out . An experimental work was performed to study the slump , unit weight, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity, dry density and chloride ion penetration test at different curing ages at 7, 14 and 28 days of concrete. Investigation on concrete properties with various % of glass powder (0%, 5%, 10%, 15% and 20% ) were done on fresh and hardened concrete. The complete stress-strain behaviour, mechanical strength and durability properties of concrete with partial replacement of natural river sand by glass powder were investigated through standard tests.The optimum glass powder content is found out by testing the specimens prepared using different grades of concrete (M20, M30, M40,M50 and M60). All the fresh concrete mixes were tested also for the workability properties by conducting slump cone tests. According to the test results, it is observed that the slump value of fresh concrete increase gradually with % of glass powder upto 40% replacements. The gradual increase in compressive strength, flexural strength and split tensile strength with the addition of waste glass powder upto 30% was observed. The addition of 40% and 50% replacements, the strength values of concrete are comparable with that of the control mix. The density and modulus of elasticity of concrete also gradually increases from 0% to 50% addition of glass powder in the concrete. The Rapid Chloride Penetration Test (RCPT) test results show that the chloride penetration rate is considerably reduced with addition of glass powder and permeability properties of concrete is enhanced upto 50% replacement levels. In order to prepare the concrete with compressive strengthThe optimum glass powder content is found to be 50% can be used as the replacement material for fine aggregates without much compromise on the strength and durability properties and to achieve economic and environmental benefits

Effect of silica fume on durability of self-compacting concrete made with waste recycled concrete aggregates

Due to adhered mortar in recycled concrete aggregates, some of the properties of concrete made with these types of aggregates, such as water absorption, porosity, electrical resistivity, and chloride ion penetration, may be affected. In this study, silica fume was used as a part of cementitious materials to improve the properties of self-compacting concrete (SCC), which were made with fine and coarse recycled aggregates. Three series of mixtures were made in the laboratory. In the first and second series, coarse recycled aggregates with replacement of 25%, 50%, 75% and 100% were used with and without silica fume. In the third series, 25% of fine recycled aggregates were replaced with fine natural aggregates. Slump flow and J-ring tests were considered for fresh state of SCC. The compressive strength, water absorption, ultrasonic pulse velocity, electrical resistivity, and chloride ion penetration tests were performed for hardened concrete. The use of silica fume improved the properties of fresh SCC. The results showed that silica fume can reduce water absorption and porosity. The silica fume showed that can resulted in a significant increase in electrical resistivity. On the other hand, the replacement of 25% of recycled aggregates did not have a significant effect on electrical resistivity, the electrical resistivity decreased by increasing the amount of replacement. Silica fume was very effective in controlling chloride ion penetration and reducing total charge passed. Silica fume also controlled the temperature of the solutions used during the test which indicates the control of the movement of ions in the penetration into concrete.

The properties of hydrophobic concrete prepared by biomimetic mineralization method

In this study, the calcium hydroxide, an inherent product of cement hydration, was treated using biomimetic carbonation method of incorporating stearic acid to generate the hydrophobic calcium carbonate on concrete surface. Carbonation reaction was carried out at various CO2 pressure and temperatures and utilizing the Scanning Electron Microscope (SEM), chloride-ion penetration test apparatus, and compression test machine to investigate the hydrophobicity, durability, and mechanical properties of the synthesized products. Experimental results indicate that the calcium stearate may change the surface property of concrete from hydrophilicity to hydrophobicity. Increasing reaction temperature can change the particles from irregular shapes to needle-rod structures with increased shear stress and thus favorable to hydrophobicity and microhardness. The contact angle against water for the concrete surface was found to increase with increasing CO2 pressure and temperature, and reached to an optimum value at around 90oC. The maximum static water contact angle of 128.7 degree was obtained at the CO2 pressure of 2 atm and temperature of 90oC . It was also found that biomimetic carbonation increased the permeability, acid resistance and chloride-ion permeability of the concrete material. These unique results demonstrate that the needle-rod structures of CaCO3 synthetized on concrete surface could enhance hydrophobicity, durability, and mechanical properties of concrete.

Durability properties of alkali pozzolan cement (APC)

This paper compares the durability properties of alkali pozzolan cement (APC) with high volume fly ash (HVFA) cement and ordinary Portland cement (OPC). The susceptibility to durability issues was investigated through the water absorption test using 28-day-old samples. Durability against chemical attacks was investigated through sulphuric acid attack, chloride ion penetration and carbonation tests on 1-year-old samples. The results indicated that APC occupies a median position in relation to OPC and HVFA, having greater resistance than HVFA for water absorption and carbonation, and greater resistance than OPC for sulphuric acid attack and chloride ion penetration. Chemical and microstructural reasons for the above behaviours are presented. A key index of durability performance is the free calcium hydroxide available and/or generated during cement hydration and durability exposure.

Durability properties of cleaner cement mortar with by-products of tire recycling

This study investigates using rubber-fiber powder (RFP), which is by-products of tire recycling, as an additive in a cement-based mortar. Five different RFP ratios of 5, 10, 15, 20, and 25% were used in this study as an additive filler side by side with reducing the cement content by the same amount. In addition to the fresh properties and the heat of hydration, the physical characterization of the rubberized mixtures including the compressive, and flexural strength the hardened density, absorption, and air voids were investigated. The results were compared to those where the cement content was reduced without adding the RFP as well as a reference mortar mixture having 0% RFP. To evaluate the new rubberized mortar as a reinforcement corrosion protector, the bulk and surface electrical resistivity, the accelerated carbon dioxide penetration, and the rapid chloride ion penetration tests were determined. Although there was a reduction in some of the mechanical characterizations, this study revealed that the recycled rubber-fiber powder could be used in the mortar as an additive to provide more corrosion resistance and less heat of hydration compared to the control mixture. Adding the RFP lowered and delayed the peak temperature for the heat of hydration compared to reducing the cement content only. From the durability side, mortar mixtures with up to 20% RFP showed an improved reinforcement corrosion resistance by increasing both bulk and surface electrical resistivity.

Sustainability of cement-stabilised clay: sulfate resistance

Sulfate attack on cement-stabilised soil is a durability problem which is directly related to the sustainability of the foundations. In this study, an experimental framework was established to evaluate the effects of sulfate attack on the strength and penetrability properties of cement-stabilised kaolin clay. Specimens incorporating ordinary Portland, pozzolanic and sulfate-resistant cements were compacted by standard Proctor effort, later cured for 1, 7, 28 and 90 d. Sodium and magnesium sulfates were used at concentrations of 0·3, 0·5 and 1%. At the end of the curing periods, the strength and penetrability characteristics of specimens were determined by conducting unconfined compressive strength and chloride-ion penetration tests. The results revealed that increase in cement content and curing time led to evident increase in strength and decrease in penetrability. Moreover, magnesium sulfate salt adversely affected hydration bonding between soil and cement in stabilised specimens. Increase in cement content caused increases in unconfined compressive strength; however, the rate of strength gain decreased in specimens exposed to sulfate attack. After 7 d of curing, the penetrability of specimens incorporating normal Portland cement is lower compared with that of other specimens including other types of cements; nevertheless, the reverse situation is valid after 28-d curing.

Ceramic waste powder an alternative cement replacement – Characterization and evaluation

In a rapidly growing world population and toward meeting consumers' needs, solid waste landfills will continue receiving extensive volumes of waste. Transforming large amount of solid wastes into an alternative resource will preserve the reducing nonrenewable resources of materials; maintain the required energy and in addition will help solve environmental and exhausted landfill problems. The utilization of solid waste materials in concrete, which is a predominant construction material, has attracted numerous studies especially those that can replace cement which is a major contributor to global green-house gas emissions. Ceramic tiles industry generates ceramic waste powder during the final polishing process. Ceramic waste powder (CWP) can cause soil, water and air pollution. Using ceramic waste powder (CWP) as an alternative ingredient in concrete will have a positive environmental impact. The aim of this study was to characterize the CWP with respect to its composition, morphology and activity. Also, the study evaluated the use of CWP as an alternative ingredient partially replacing cement on the performance of fresh and hardened concrete. In this investigation, concrete mixtures incorporating CWP as cement replacement with different replacement levels (i.e., 10%, 20%, 30% and 40% by mass) were examined. Three concrete grades with different cement contents were used (i.e., 25 MPa, 50 MPa and 75 MPa). The fresh concrete workability retention of the mixtures was evaluated by measuring time to reach zero slump. Compressive strength development with age (i.e., 7, 28 and 90 days) and drying shrinkage strain at 120 days were measured. The chloride ion penetration (i.e., rapid chloride ion penetration test - RCPT) and bulk electrical resistivity were conducted to evaluate durability performance of the mixtures. The permeable pores were measured to assess the development in the concrete microstructure. Test results showed that CWP has potential to be used as an ingredient in concrete mixtures to partially replace cement. The study showed that concrete mixtures with ceramic waste powder (CWP) had variable performance of the measured properties depending on the replacement level used. In general, CWP can be used in concrete mixtures to partially replace cement and improve specific performance criteria. A performance index (PI) approach was developed in order to be able to select the suitable CWP replacement level to optimize the mixture's specific properties to achieve a desired performance criteria. In this study, the PI considered workability retention, compressive strength and durability as performance measures for selecting the most suitable CWP replacement level. The PI could be extended to include additional criteria. The use of 10% CWP replacement level was adequate for strength improvement, replacement levels between 10% and 20% could be used to improve workability retention while a level of 40% replacement was needed for durability enhancement. For more than one performance criteria the CWP replacement level varied; a 10% to 20% CWP was suitable for optimizing the workability retention and strength of the mixture. However, the use of 30% to 40% CWP would optimize the combination of all studied criteria.

Effects of Reinforcing Fiber and Microsilica on the Mechanical and Chloride Ion Penetration Properties of Latex‐Modified Fiber‐Reinforced Rapid‐Set Cement Concrete for Pavement Repair

This study evaluated the influence of reinforcement fiber type and microsilica content on the performance of latex‐modified fiber‐reinforced roller‐compacted rapid‐hardening cement concrete (LMFRCRSC) for a concrete pavement emergency repair. Experimental variables were the microsilica substitution ratio (1, 2, 3, and 4%), and the reinforcement fiber (jute versus macrosynthetic fiber). In the tests, compressive, flexural, and splitting tensile strength; chloride ion penetration resistance; and abrasion resistance were assessed. From the compressive and flexural strength tests with microsilica substitution, the 4‐hour curing strength decreased as the microsilica substitution ratio increased. From the chloride ion penetration test, as the microsilica substitution ratio increased, chloride ion penetration decreased. The abrasion resistances increased with the substitution ratio of microsilica increase. Based on these test results, microsilica at a substitution ratio of 3% or less and macrosynthetic fiber as the reinforcement improved the performance of LMFRCRSC for a concrete pavement emergency repair and satisfied all of the target strength requirements.

Strength and durability study of sulphur concrete with replaced fine aggregate

Increase in the technologies and concern about the environmental issues in the present world has led to the requirement of a new construction material which does less harm to the environment and also utilizes the available waste material. Sulphur concrete is type of concrete where cement and water is not used instead melted sulphur which act as binding agent is used to bind the fine and coarse aggregate and the filler material like fly ash together to form a hard concrete. There for study on varies properties of sulphur concrete is very much essential to relate it with normal cement concrete. In this paper various mechanical and durability of sulphur concrete is done. Along with determining a sulphur concrete mix, sulphur concrete with different fine aggregate like beach sand, eco sand and manufactured sand replacing river sand in 0%, 25%, 50%, 75% and 100% is also studied. Durability of sulphur concrete of each type fine aggregate with best compressive strength is also studied. Water absorption, resistance to different chemical environments and rapid chloride ion penetration test is done to determine the superiority of sulphur concrete over cement concrete. Result shows that sulphur concrete can be used in areas subjected to heavy moisture content, where acid activities are more. Strength wise SC give similar result to normal concrete. Another advantage of sulphur concrete is that any type of fine aggregate can be used as filler in SC since it is a water repellent type concrete.

The effect of steam curing on chloride penetration in geopolymer concrete

In this paper, we present the result of our study on the effect of steam curing to chloride ion penetration in geopolymer concrete. Class F fly ash was activated using sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3 ). The concrete specimens were then steam-cured at 40°C, 60°C, 80°C and room temperature at 24 hours. The treatment was followed by wet curing for 28 days, and then followed by immersion of all specimens in salt water for the durations of 30, 60, and 90 days. Cylindrical specimens were then prepared for compressive strength, chloride ion penetration, pH, and porosity tests. A 16 mm-steel bar was fixed at the center of the specimen concrete blocks (specimen size: 10cm × 10cm × 15cm). Corrosion probability was determined by conducting Half Cell Potential test. Our result showed that increasing the curing temperature to 80°C induced chloride ion penetration into the concrete’s effective pores, despite improvements in compressive strength. We also found that chloride ingress on the geopolymer concrete increases commensurately with the increase of the curing temperature. The corrosion potential measurement of geopolymer concrete was higher than OPC concrete even if corrosion was not observed in reinforcing. Based on our result, we suggest that the corrosion categorization for geopolymer concretes needs to be adjusted.

Mechanical and durability properties of high performance glass fume concrete and mortars

Based on its high content in amorphous silica (SiO2>70wt.%), waste glass is an excellent material for valorization into pozzolanic nanoparticles or the so-called “glass fume” (GF). GF, produced using a scalable radiofrequency induction-coupled-plasma (RF ICP) spheroidization technology, mainly consists in an emulation of silica fume (SF) composed of spherical and amorphous silica-based nanoparticles (dia. of 30–200nm). To test the impact of GF on the mechanical and durability properties of cement-based materials, compressive strength and rapid chloride ion penetration tests (RCPT) were conducted on high-performance concrete (HPC). Meanwhile, measurements of the resistances to alkali-silica reaction (ASR) and to sulfate attack were performed on mortar bars.As SF, GF increased the compressive strength of HPC at early age (<7days) by its nucleation and filler effects, but also its high alkali content (11–12wt.%). At late age (>28days), GF is characterized by a slower pozzolanic reactivity than SF. However, GF-contained HPC achieve similar compressive strength than SF-contained HPC after 91days of curing.At early age, GF-contained HPC and mortars yielded lower durability properties (RCPT, ASR and sulfate attack) than SF-contained HPC and mortars due to the slower pozzolanic reactivity of GF. In fact, they yielded similar durability properties compared to the plain cement HPC and mortars (control mixtures). At late age, the alkalinity of the pore solution is reduced and the cement paste is densified by the pozzolanic calcium silicates hydrates (C-S-H) and the durability properties are greatly improved with respect to a control HPC.

Influences of steam and autoclave curing on the strength and chloride permeability of high strength concrete

This paper presents the results of an experimental investigation carried out to evaluate the influences of curing methods and mineral admixtures on the strength and chloride permeability of concrete. Rapid chloride ion penetration tests (ASTM C 1202) were used to measure the chloride permeability of concrete. Test results indicated that steam curing decreased the 28 days compressive strength of plain concrete by 11 %. Incorporating slag, fly ash, and silica fume can significantly mitigate this harmful consequence. After autoclave curing however, all concrete’s strength exceeds 80 MPa. Steam and autoclave curing increase the electrical charge passed through plain cement concrete by 110 and 224 %, respectively, when compared with normal curing. For steam curing, incorporating silica fume is the most efficient means to reduce the chloride permeability of concrete. For autoclave curing however, incorporating 30 % fly ash is the most efficient means to reduce chloride permeability.

Assessment of the effect of sulfate attack on cement stabilized montmorillonite

In this study, aiming to investigate the effects of sulfate attack on cement stabilized highly plastic clay; an experimental study was carried out considering the effects of cement type, sulfate type and its concentration, cement content and curing period. Unconfined compressive strength and chloride-ion penetration tests were performed to obtain strength and permeability characteristics of specimens cured under different conditions. Test results were evaluated along with microstructural investigations including SEM and EDS analyses. Results revealed that use of sulfate resistance cement instead of normal portland cement is more plausible for soils under the threat of sulfate attack. Besides, it was verified that sulfate concentration is responsible for strength loss and permeability increase in cement stabilized montmorillonite. Finally, empirical equations were proposed to estimate the unconfined compressive strength of cement stabilized montmorillonite, which was exposed to sulfate attack for 28 days.

미생물을 혼입한 콘크리트의 전기적 염화물 침투 저항 및 강도 특성 평가

In recent years, river sand depletion has caused the increase of sea sand use. Chloride which exists in the sea sand promotes the rebar corrosion and causes degradation of durability in the RC concrete structures. In case of offshore RC structures, chloride causes the rebar corrosion and the salt damage which generates concrete cracks, although high quality river aggregates are used for the building construction. In this study, the concretes were produced by using a microorganism and the compressive strength test and the chloride ion penetration test were performed. Two tests(compressive strength, chloride ion penetration resistance) were carried out for performance evaluation of concrete. <TEX>${\phi}100mm{\times}200mm$</TEX> size specimens were made and 5 types of mixing water(2F-1, 5B, Urea medium, Marine broth medium and Ordinary water) were used to make concrete specimens and compressive strength test. All specimens were cured for 7, 28days. To evaluate chloride ion penetration resistance, <TEX>${\phi}100mm{\times}200mm$</TEX> specimens were cut and <TEX>${\phi}100mm{\times}50mm$</TEX> samples were prepared. The electrical chloride ion penetration testing method were performed in order to measure the chloride ion resistance and the test was progressed according to the contents of ASTM C1202-12. SEM and porosimeter analysis were performed in order to identify the microstructures of specimens. As a result of the tests, 2F-1 group had superior compressive strength and chloride ion penetration resistance to the others. Through this research, it was tried to examine the potential for reducing the defects of concrete and applying the micro-organism as a natural admixture material.

Durability-related performance of concrete containing fine recycled aggregates from crushed bricks and sanitary ware

Information on the effects of incorporating fine recycled ceramic aggregates on concrete's durability is very scarce. This paper presents an experimental study using aggregates sourced from crushed red clay ceramic bricks (CBAs) and sanitary ware (SWA). Different concrete mixes were produced where the fine natural aggregate fraction was partially or fully replaced (20%, 50% and 100%, by volume) by each of these materials. Shrinkage, water absorption by immersion, water absorption by capillary action, carbonation and chloride ion penetration tests were carried out. Results show that using fine CBA provides better performance in terms of water absorption by capillarity and chloride ion penetration, contrarily to shrinkage, water absorption by immersion and carbonation penetration. Using fine SWA leads to a similar performance in terms of shrinkage, but all other properties are significantly and detrimentally affected. Notwithstanding the increased water requirement due to the high absorption capacity of CBA and the formation of agglomerated particles with SWA, this paper shows that a judicious use of these materials may allow the production of adequate structural concrete; in mixes with SWA the use of superplasticizers is a very effective approach in preventing the formation of clusters, even providing a better performance than the control concrete.

Evaluation of the Different Test Methods of the Concrete Durability for the Persian Gulf Environment

Environmental conditions of the Persian Gulf in terms of the durability of the reinforced concrete structures are highly aggressive and corrosive. Hence, in the Persian Gulf and Oman sea areas, based on the national code of practice, concrete durability is controlled by water absorption, water permeability and rapid chloride ion penetration tests. In this research, the above three mentioned tests plus total water absorption test, electrical resistivity, and capillary sorption tests were performed on 216 samples from six concrete mixtures with different water to binder ratios and pozzolan content (fly ash and silica fume). Based on the experimental results, the total water absorption and the water permeability tests were the most and the less accurate tests respectively. Results also showed that the capillary sorption test can be used as a suitable method to evaluate the concrete durability in the marine areas. In this study also a relationship between the specific limits of these tests for different environmental conditions was proposed.

RETRACTED: Comparative study on effects of Class F fly ash, nano silica and silica fume on properties of high performance self compacting concrete

Abstract This paper presents the effects of some admixtures including silica nanoparticles, silica fume and Class F fly ash on different properties of high performance self compacting concrete (HPSCC). For this purpose, a fraction of Portland cement with the aim of cement content reduction was replaced different fractions of pozzolanic admixtures. The rheological properties of fresh concrete were observed through slump flow time and diameter and V-funnel flow time. Thermal properties were investigated via thermogravimetric analysis (TGA) test. Transport properties evaluated by water absorption, capillary absorption and chloride ion penetration tests. The results indicated that increase of fly ash content improves the rheological properties of HPSCC. The results also showed that mechanical and transport properties improved in the mixtures containing admixtures especially blend of silica nanoparticles and silica fume. It can also be concluded that higher amount of mineral admixtures combined with small fractions of nanopowders could be promising technique toward high performance concrete as a key material along with energy saving in construction and building technology.

Use of Furnace Bottom Ash for producing lightweight aggregate concrete with thermal insulation properties

The influence brought by Furnace Bottom Ash (FBA) incorporation on the properties of lightweight aggregate concrete was studied systematically. In total, six mixtures of concrete targeted at a 28 d compressive strength of 30 MPa were designed, including one control mix made with all normal weight aggregates and at a water/cement ratio (w/c) of 0.6, and another five lightweight aggregate concrete mixes at a w/c of 0.39 by using 0, 25%, 50%, 75% and 100% FBA replacing natural fine aggregate (crushed fine stone). The testing results of the hardened concrete properties showed that, for the lightweight aggregate concrete using 100% FBA to replace crushed fine stone, a 28 d oven-dried density of about 1500 kg/m3 was obtained. The test results showed the lightweight aggregate concrete had lower strength and stiffness compared to the normal aggregate concrete. But in terms of the effectiveness of strength provided by unit weight of concrete indicated by compressive strength in MPa divided by saturated-surface dried (SSD) density in g/cm3, fc/D, a satisfactory ratio can be obtained when not more than 50% FBA was used to replace the crushed fine stone. The durability property indicated by the chloride ion penetration test shows the lightweight aggregate concrete with FBA had high chloride ion penetrability. The heat insulation property (thermal conductivity K-value) test demonstrated that by using the porous lightweight aggregate, the thermal conductivity could be lowered to around 70% of the control. When more FBA was used to replace crushed fine stone, the thermal conductivity value could be further reduced. The results of this study demonstrated it is feasible to produce lightweight aggregate concrete with high volume of FBA incorporation for building insulation uses.

Mechanical and Durability Properties of Medium Strength Self-Compacting Concrete with High-Volume Fly Ash and Blended Aggregates

This research investigates the fresh state properties and hardened state properties of medium strength, self-compacting concrete incorporating a high volume of class F fly ash as a partial replacement to cement and blended fine aggregates while maintaining satisfactory properties of SCC. The properties of self-compaction investigated are: slump flow, J-ring, L-box, Vfunnel, sieve stability and Visual Stability Index tests. Those of hardened concrete include compressive strength, splitting tensile strength, complete immersion water absorption, apparent volume of permeable voids, sorptivity, and rapid chloride ion penetration tests. The experiments on fresh state properties investigate the filling ability, the passing ability and the segregation resistance of concrete. The results show that fly ash improves workability and decreases the compressive strength as well as splitting tensile strength. Fly ash based SCC shows better resistance to water absorption, apparent volume of permeable voids, sorptivity, and chloride penetration than the control mix.

슬래그 혼입량이 슬러리형 급결제를 활용한 숏크리트 몰탈의 물성에 미치는 영향

숏크리트의 필수 구성요소 중 하나인 급결제는 높은 pH환경에서 거동하는 경우가 많고 이를 억제하기 위해 개발된 시멘트 광물계 분말형 급결제 또한 작업시 다량의 분진 발생으로 인하여, 여러 환경적 문제를 일으키고 있다. 본 연구에서는 이러한 문제점을 해결하기 위하여 슬러리형의 급결제를 도입하고, 기본적인 물성 파악을 위해 숏크리트 배합에 혼화재로서 자주 활용되는 슬래그의 혼입에 따른 숏크리트 재료의 응결 및 경화특성, 강도 특성 및 염화물 이온 침투 저항성을 평가하였다. 슬래그의 혼입에 따른 응결 경화의 촉진 및 1일 압축강도의 발현은 <TEX>$C_{12}A_7$</TEX>과 황산칼슘의 수화반응에서 생성된 에트링가이트상의 양과 관련이 있는 것으로 보이며, 3일 강도 이후의 물성은 일반적인 규산3칼슘의 수화반응과 관련이 있는 것으로 나타났다. 염화물 이온침투 저항성의 경우, 슬래그의 혼입량이 증가하면 훨씬 개선되는 것으로 나타나, 향후 이러한 배합에 대한 내염해성의 정밀한 평가가 필요한 것으로 나타났다. The set accelerator used for shotcrete at high pH environment often causes the dusting problem in practice. In this research, a slurry-type set accelerator was developed to avoid this problem and its effectiveness was investigated by applying it to shotcrete mortars. Set time, stiffening, compressive strength, and chloride ion penetration resistance were examined with different amounts of slag, used as partial replacement of cement. According to the experimental results, it was found that the earlier responses such as set time, stiffening, and 1-day compressive strength were probably affected by the amount of ettringite, formulated by the hydration between C12A7 and calcium sulfate polymorphs present in blast furnace slag. Whereas, it is believed that the result of compressive strength after 3 days was attributed to the hydration of tricalcium silicates. As for the results of a chloride ion penetration test, the partial replacement of cement with slag significantly reduced the total charge passed through the shotcrete mortar.